Galactic nuclei luminosity: A model of steady spherically-symmetric accretion of optically-thick gas on to Kerr black holes

Abstract

Stationary spherically-symmetric accretion on to Kerr black holes is studied. A theoretical model has been developed in which the relativistic equations of continuity, conservation of four-momentum, local energy balance, and synchrotron radiative transfer have been integrated, by means of a combination of analytical and numerical procedures. A special emphasis has been put on evaluating the outcoming fluxes, as they can be compared with observations. Calculations were performed for masses of black holes in galactic nuclei, 106M⊙ as representative of the hypothetical black hole in the nucleus of the Milky Way and 107M⊙ as representative of a moderate Seyfert nucleus. The emergent spectra differ considerably from observations, as they are severely modified by dust in more external regions. The total frequency-integrated luminosity is, however, in very good agreement with observations.